Poppet valve with wear resistant stem tip



April 1962 M. J. TAUSCHEK 3,028,479

POPPET VALVE WITH WEAR RESISTANT STEM TIP Filed Oct. 10, 1958 2 Sheets-Sheet 1 51 i J LYEEZTQJP Max M YZIusa/Iek April 1962 M. J. TAUSCHEK 3,028,479

POPPET VALVE WITH WEAR RESISTANT STEM TIP Filed Oct. 16, 1958 2 Sheets-Sheet 2 Max (I Ruse/26k b Kl! ZLZLHE United States Patent l Filed Oct. 10, 1958, Ser. No. 766,442 Claims. (Cl. 219-76) The present invention relates broadly to poppet valves, and is more particularly concerned with a new and improved valve and method of producing the same featuring the provision on the valve stem of a fusion welded tip having superior resistance to wear, spalling and scufling.

only and as forged structures with a finer grain size somewhat reduce the tip problem, the results obtained therefrom leave much room for improvement. Again, omission of the solution heat treatment comprises other desirable properties of the material, particularly the hot creep strength. Austenitic materials in general exhibit relatively poor tip properties as a result of a heterogeneous structure, a large grain size, and a soft matrix With hard areas of massive carbide precipitation. Further, the average tip hardness frequently varies from 18 to 38 Rockwell C, and this condition is a secondary. contributing factor to poor tip perforance.

Various solutions have been proposed and effected, and among those which are known are the addition of wear buttons, tip cups and the like to the engine. Such expedients possess the obvious disadvantages of complicating the engine assembly, as well as the danger of becoming detached and damaging the engine. A further solution which has been used with some measure of success is to butt or flash weld a short stem end of hardenable ferritic alloy to the valve tip; however, this method is relatively expensive from both a material and processing standpoint, and gives rise to the problem of maintaining uniform weld quality.

It is accordingly an important aim of the present invention to provide a new and improved poppet valve having a stem tip characterized by superior resistance to wear, spalling and scufling.

Another object of this invention lies in the provision of a method of substantially reducing valve stem tip failures, which method is particularly suitable in large scale production operations.

Still another object of the invention is to provide a fusion welded tip on poppet valve stems, the tip material being a relatively inexpensive wire produce which is hard as deposited to thereby eliminate a separate subsequent heat treatment.

A still further object of the invention is to provide a method of welding a highly wear resistant material onto a valve stem tip which eliminates the need of first recessing the tip end to receive an insert nubbin, and which additionally utilizes a tip material employable on both ferritic and austenitic valve base materials.

Other objects and advantages of the present invention 3,628,479 iatented 'Apr. 3, 1962 will become more apparent during the course of the following description, particularly when taken in connection with the accompanying drawings.

In the drawings, wherein like numerals are employed to designate like parts throughout the same:

FIGURE 1 is an elevational view of welding apparatus effective to perform the method of this invention;

FlGURE 2 is a partial elevational view of apparatus similar to that of FIGURE 1, and showing the .electrode of the apparatus in an off-center position with respect to the stem tip of a coolant filled valve;

FIGURES 3 and 4 are detail sectional views showing the weld formations obtained by utilization of the apparatus of FIGURES 1 and 2 respectively;

FIGURES 5 and 6 are detail sectional views of finished valvestem tip portions after grinding or removing the excess weld deposits of FIGURES 3 and 4;

FIGURE 7 is a reproduction of a photomacrograph of the stem tip portion identified as FIGURE 3; and

FIGURE 8 is a reproduction of a photomicrograph showing the crystalline structure of the weld and base materials produced in accordance with the teachings of this invention.

Briefly stated, the present invention is directed to a poppet valve and method of producing the same featuring the provision on the valve stem end of a fusion welded tip characterized by markedly increased wear, spalling and scuffing resistance. The tip material may be applied with speed and ease to valve bases having either ferritic or austenitic analyses, and is itself preferably possessed of properties such thata Rockwell C hardness of about is obtained in the as cast form without additional heat treatment. The micro-crystalline structure of the preferred tip material as fusion welded to the valve stem includes pseudo-hexagonal chromium carbides, martensite, and a fine carbide dispersion in austenite. The valve tip is compatible with known rocker arm materials.

Various forms of apparatus may be employed to produce the novel article of this invention, and preferably an automatic fusion welding machine is employed utilizing a high frequency alternating current superimposed on a direct current. The valve is rotated to achieve weld uniformity, and the welding eletrode may be positioned in alignment with the valve stem axis or off-center therefrom. In either case, the juncture between the tip material and originally fiat stem end is curved when viewed in cross-section. Other features and advantages of the article and method of this invention will be brought out in the description now to follow.

The earlier solutions to valve tip failures utilizing welding techniques have largely employed hand methods. One, hardenable ferritic alloys in the form of a short stem end have been butt welded to the valve tip with far from completely satisfactory results. The method is expansive from both a material and processing standpoint, and weld quality is difficult to maintain producing in many cases a break at the juncture of the tip and stem causing the tip to be thrown into the engine with consequent damage thereto. Second, and particularly with aircraft valves, a recess has been provided within the circumference of the stem and a high carbon cobalt'base alloy insert nubbin of harder characteristics than the stern metal integrally united to the stern throughscale production techniques required for automotive applications. Third, cast Stellite rods have been fusion welded by hand methods to valve stem ends, but clearly this method again is highly uneconomical when large quantities are required.

Each of the foregoing objections and disadvantages of the earlier methods are avoided by the process of this invention, which involves essentially supporting a plurality of either solid or coolant filled valve bodies having an austenitic or ferritic analysis in an upright position upon means effective to rotate the valves, directing at least one of the valve bodies beneath an electrode supplied by current from a high frequency alternating current superimposed on a direct current, blanketing the electrode and tip area with a monatomic inert gas while drawing an are between the electrode and the valve body to melt the valve stem end and form a pool of stem material, continuing the high frequency. alternating current and direct current while feeding into the are at an angle to the valve stem end a relatively highcarbon alloy in wire form, the alloy being preferably air hardenable as cast to eliminate the requirement of additional heat treatment, the wire forming globules of metal in the pool of valve stem end material, the wire feed being then stopped while the current flow is continued to cause the alloy globules toflow over the-valve stem end and fuse thereto, whereby a tip is formed on the valve stem end characterized by superior wear, spalling and scufiing resistance.

Apparatus to perform the described method is preferably constructed to permit the use of automated techniques, and one form of apparatus is illustrated in FIG- URES l and 2, although it is to be appreciated that the device disclosed may take other forms without departure from the novel concepts of this invention. As may be seen in FIGURE 1, an exemplary automatic fusion welding machine A may comprise an elongated body portion receiving at one end a control housing 11 providing a conduit for a shield gas. connection 12, a water inlet connection 13, a current input connection 14 and a water outlet connection 15. The body portion 10 mounts means 16 to provide an attachment to supporting structure, and the end of said body portion opposite the control housing 11 carries a head portion generally designated at 17. The head portion is axially movable by suitable electronic control means in order to maintain the proper arc, and may comprise a cylindrical metallic nozzle 18 threaded or othewise secured to the body portion '10. Interiorly of the nozzle member 18 is a nozzle spacer 19 which functions in part to provide a flow chamber for an insert gas directed through openings 20 in a probe portion 21 of the Welding machine body 10. The probe portion is further apertured at 22 to provide outlets for coolant to maintain the temperature of the nozzle and related structure at a safe operating temperature. In a commercial structure, water from the inlet connection 13 passes downwardly through an outer concentric tube in the body portion 10, outwardly from the ports 22 and upwardly through an inner concentric tube in the body portion 10.

The metallic nozzle member 18 is shaped at one end with a generally hollow coneportion 23 integral with a terminal collar portion 24 mounting or supporting an electrode 25, the portion 24 being suitably interiorly apertured to permit the flow therethrough of the shielding gas. The electrode may be formed of known materials, and a virtually non-consumable tungsten electrode is suitable for this purpose.

As earlier noted, the valve body to which a Wear resistant stem tip is to be welded may be positioned in essentially precise vertical alignment with the electrode, or may be located in an oif center position relative thereto. The former arrangement is illustrated in FIGURE 1 and it may be seen that a valve body 26 having a solid stem portion 27 is supported along its head 28 upon rotatable means 2 9 with the central vertical axis of the stem 27 in anna s-'79 alignment with the corresponding axis of the electrode 5 25. The rotatable means 29 may comprise a table having individual rotatable positions, the table being additionally caused to travel in a circumferential path to position individual valve bodies beneath the welding machine A.

Weld material 30 in wire form and a composition to be later described is fed by suitable drive means R at an angle of about 15 to face 31 of stem tip 32 for a period and at a rate determined largely by the wire composition and valve body composition, specific operating conditions to be noted in a later disclosed example. As used herein,

the term wire includes a tubular member containingv area at the valve tip. Further, the block increases the solidification rate of the weld after the welding current"- is turned oil.

A tenacious bond between the weld material 30 and valve body tip 32 is also obtained when the valve is in an off-center position with respect to the electrode. This arrangement is shown in FIGURE 2, and by way of example only, is shown in connection with a valve body 33 having a stem portion 34 provided interiorly with a coolant cavity 35 into which may be inserted a quantity of sodium or the like. The valve body 33 is supported in an upright position along its head portion upon rotatable means in the manner of FIGURE 1. not specifically shown, a cooling block B of the same character as in FIGURE 1 is, employed on the stem 34. It is to be seen in FIGURE 2 that valve tip 36 is located relative to the electrode 25a such that tip face 37 has its center radially outwardly of the central vertical axis of the electrode 25a, that is, the valve stem 34 is offcenter with respect to the electrode 25a. The welding machine employed in the arrangement of FIGURE 2 is in all respects identical to that of FIGURE 1, and the suffix a has been applied to corresponding parts therein. Similarly, the weld material 30a-is identical, is fed by rolls R, and is located in the same angular relation with respect to the valve tip face 37.

The present method is of proven application in the formation of Wear resistant tips on valve bodies 26 having a solid stem portion 27, such valve bodies having essentially an austenitic structure, or hollow valve bodies- 33 which are substantially of ferritic material. Many compositions exist for both the solid and coolant filled valve bodies, and by way of illustration only, a solid valve body upon which particularly satisfactory results have been obtained has av known composition consisting essentially of 0.475 to 0.575% carbon, 20.00 to 22.00% chromium, 8.00 to 10.00% manganese, 3.25 to 4.50% nickel, 0.04 to 0.09% sulphur, 0.38 to 0.50% nitrogen, a maximum of 0.25% silicon, a maximum of 0.03% phosphorous, and the balance substantially iron. A fer: ritic material well known for coolant filled valves, and upon which a wear resistant tip may be fusion welded in accordance with this invention, has a typical composition consisting essentially of 0.76 to 0.86% carbon, 19.00 to 21.00% chromium, 1.90 to 2.60% silicon, 0.20 to 0.60% manganese, a maximum of 0.030% sulphur, a maximum of 0.030 phosphorous, and the balance substantially iron. Other compositions may of course be employed in the valve body material, with equally satisfactory results fiowing therefrom.

For large scale production operations associated with automotive valve applications, it is highly important that the weld material 30 be relatively inexpensive and. in

Further, while wire form. Further, to avoid excessive wear due to the sliding and pounding action with the engine rocker arms, the tip hardness should be at least 50 Rockwell C and be possessed of a satisfactory grain structure. In addition, it is highly desirable that the tip material be air hardenable as cast in order to avoid the requirement of additional heat treatment. While it will be found that various compositions provide satisfactory results, at present the wear problem has been essentially entirely avoided by a relatively high carbon and chromium content which in weld wire form has a typical analysis of 6.00% carbon, 2.7% manganese, 1.70% silicon, 1.08% molybdenum, 31.50% chromium, 0.55% zirconium, and the balance substantially iron. This same composition after deposition has an analysis of essentially 3.60% carbon, 1.90% manganese, 1.00% silicon, 1.00% molybdenum, 20.00% chromium, and thebalance substantially iron.

Materials are also available in wire form, which although having a hardness of 20 to 35 Rockwell C as welded, can be. brought up to about 50 Rockwell C by subsequent heat treatments. By way of example, one composition has an analysis of 0.95% carbon, 0.35% manganese, 0.10% silicon, and the balance substantially iron, while another known material has a composition consisting essentially of 1.12% carbon, 1.00% manganese, 1.00% silicon, 17.00% chromium, 0.50% molybdenum, and the balance substantially iron. A further alloy which provides a highly wear resistant tip has an analysis of approximately 0.80% carbon, 0.75 manganese, 0.75% silicon, 3.75% chromium, 1.55% tungsten, 8.70% molybdenum, 1.15% vanadium, and the balance substantially iron. In addition, it is known that sub stantial improvement in tip wear resistance is obtained by a composition consisting essentially of 1.00% carbon, 0.40% manganese, 0.30% silicon, 5.25% chromium, 1.15% molybdenum, 0.40% vanadium, and the balance substantially iron. are in the weld wire form.

To provide a highly wear resistant tip upon a valve body, said body is located with respect to the electrode 25 in either of the positions shown in FIGURES 1 and 2. An inert gas such as argon is flowed through the connection 12 along the axis of the Welding machine body portion and outwardly from the openings 20 in the probe member 20 to issue from the terminal collar portion 24 in blanketing relation to the electrode 25 and stem tip 32. High frequency alternating current generated by a spark-gap oscillator and superimposed on a direct current is transmitted through the current connection '14 to the electrode 25 to start the arc. stem tip material is thereby melted and forms a pool of said material, after which the wire feed is initiated to direct the wire into the arc and form globules of weld wire in the pool of tip material. After a predetermined period, the wire feed is stopped, the welding current being continued, and the globules are caused to flow over the valve tip and fuse thereto.

Specific applications will of course dictate variations in the operating conditions employed, and by way of specific example, there is set forth in tabular form below the conditions utilized to weld 0.360 inch diameter valve stems formed from an austenitic material having a composition consisting essentially of 0.475 to 0.575% carbon, 20.00 to 22.00% chromium, 8.00 to 10.00% manganese, 3.25 to 4.50% nickel, 0.04 to 0.09% sulphur, 0.38 to 0.50% nitrogen, a maximum of 0.25% silicon, a maximum of 0.30% phosphorous, and the balance substantially iron. The weld wire, onthe other hand, had the composition earlier noted in wire form of essentially 6.00% carbon, 2.70% manganese, 1.70% silicon, 1.08% molybdenum, 31.50% chromium, 0.55% zirconium, and the balance substantially iron. I: is to be noted that the table reflects the operating conditions when the valve body was in both a solution treated, and a solution treated and aged form.

The

Each of the four analyses mentioned Table 1 Solution Sol. Treated Treated and Aged Valve, r.p.m 18 18 Argon Flow, c.f.h 25 25 Wire to electrode distance, inches l V4 Wire feed rate, inches/minute 133 4 16 Wire teed time, seconds 10 7% Cooling block to tip distance, inch 0. 029 0. 029 Amperage setting Elect-rode to work distance, inches Vs Zia Angle between filler wire and tip face, degrees 15 15 Preheat; time, sec 1-2A Post heat time, sec 924 FIGURE 3 is a view showing the weld deposit formed when the electrode 25 is in the on-center position of FIGURE 1, while FIGURE 4 shows the weld deposit produced when the electrode is ofi-center with respect to the stem axis in the arrangement of FIGURE 2. It is to be seen that as produced and prior to a grinding step weld material 38 on stem 27 in FIGURE 3 is essentially convex as at 39, and that axially inwardly therefrom a concave recess 40 is formed by action of electrode 25 and a weld bond formed therewith by an essentially convex central inner portion 4'1 of the weld material 30. It is to be further seen that adjacent the outer diameter of the valve stem the tip face is generally rounded to provide a smoothly curved annular marginal portion 42, and that the weld material 38 as initially deposited is of greater diameter than the valve stem 27.

The macro-crystalline structure of the weld deposit 38 and upper end of the stem 27 is shown in FIGURE 7, and it is to be noted that the weld bond line in the central portion is of relatively greater axial thickness, as indicated by the numeral 43, than radially outwardly toward the rounded annular portion 42. The photoreproduction of FIGURE 7 is at a magnification of X 9.

FIGURE 4 shows the weld deposit formed on the stem 36 of a valve body 34 when the electrode 251: is in the off-center position of FIGURE 2. Weld deposit 44 is convex along upper surface 45', and by rotation of the valve body 34 an annular groove 46 is formed on the end face, the outer diameter of the annular recess being radially inwardly of the circumference of the valve stem. Accordingly, at essentially the center of the stem tip face the weld deposit is substantially concave as indicated by the numeral 47, and the stern tip face has a raised or concave portion 48 at generally the center thereof. While not shown in a separate photomacrograph, the weld bond line between the deposit and the base alloy is relatively greater at the bottom of the recess 46 and decreases in thickness toward both the center of the valve stem and radially outwardly toward the outer circumference thereof.

Subsequent to application of the weld deposits 38 or 44 to the valve stems 27 or 36, respectively, the valve bodies are further processed and this includes grinding or otherwise removing a portion of the deposits 38 or 44 to produce an essentially finished valve configuration of the character shown in FIGURES 5 and 6. It is to be noted from FIGURE 5 that the weld deposit 38 is ground around its circumference to remove the portions which overlap the valve stem outer diameter, and the deposit may be ground to provide on the tip beveled corners 49. It is to be further seen that valve tip weld material 50 essentially entirely covers the exposed surface of the valve stem end so that rocker arm contact will be made only with the highly wear resistant tip portion 50. Also, it is to be noted that valve 51 when finished carries the tip weld material 50 in a generally concave recess 52;, and accordingly the central portion of the weld material is essentially convex as denoted by the numeral 53. In accordance with customary practice, a stem groove 54 may be provided on the valve stem to receive suitable valve spring retainer means.

Referring now to FIGURE 6, which shows the valve spasms stem 36 upon completion of suitable finishing operations, it is tobeseenthat valve 55 may also'be provided with beveled corners 556 at the valve stem tip portion, and that the weld material '7 essentially completely covers the outer end of-the stem portion, for the purpose stated in the previous. paragraph. The weld material 57 is bonded to the valve stem materialalong a complexly curved line, and byaction of the off-center electrode, an annular groove 58 isforme'd which connects at the center of the valve stemend with a raised portion 59. The weld material 57 forming a'highly wear resistant tip on the valve body 55 accordingly has an annular convexly curved lower surface 6%, which meets with the-annular groove 58. As noted also in the, preceding paragraph, a stern groove 61 may be provided to receive the conventional valve spring retaining means.

The micro-crystalline structure of the new and improved valve of this invention is shown in FIGURE 8, to which reference is now made. It is to be seen in the photoreproductiomthe original of which was taken at a magnification of X 100, that the weld material identitied at the upper end of the view by the legend W is characterized by psendo-hexagonal chromium carbides 62, dark area martensite 63, and fine carbide dispersion in austenite designated at 64. The Weld bond line is identified in FlGURE 8 by the numeral65, andthe base material therebeneath by the legend B. The base material displays, as designated by the numeral 66 austenite in the heat-affected zone, and a regular austenitic structure, as identified by the numeral 67. It is to be further noted that the austenite 66 in the heat affected Zone and the regular austenitic structure 67 in the base material B includes carbide and sulfide dispersions. illustrative of the new and improved results obtained by the poppet valve of this invention, are the results of engine tests which havebeen run under strenuous operating conditions employing'a tipped valve produced as herein disclosed, and utilizing as the tip material a composition consisting essentially of 6.00% carbon, 2.70% manganese, 1.70% silicon, 1.08% molybdenum, 31.50% chromium, 0.55% zirconium, and the balance substantially iron, the percentages of elements being the alloy in weld wire form prior to deposition. The tests were run utilizing as the rig engine a Chevrolet V-8 operating at an engine speed of 4500 r.p.m. for a duration of 500 hours. The valve lash was 0.010 inch and the oil temperature approximately 200 F. It was found that the wear'which occurred on the valve tips during the 500 hour period was insignificant, with a maximum value of 0.0016 inch. Further, the rocker arm contacting surface showed no significant wear. There was in addition no indication whatsoever of a loosening of the bond between the weld and base materials.

It is to be seen from the foregoing that applicant has completely avoided the problems associated with earlier attempts to avoid valve tip failures. There is no longer the necessity of adding wear buttons, tip cups or the like to theengine which complicate the engine assembly, nor a need to butt or flash weld a short stem end of hardenable ferritic alloy to the valve stem and run the risk of tip breakage during use and consequent engine damage. The-method of this invention may be practiced with substantial speed, making it of particular importance in large scale automotive component production, and by utilization of the preferred weld material there is eliminated the requirement of additional heat'treatment to obtain the desired tip hardness. The preferred weld material has a Rockwell C hardness of at least 50 and possesses a satisfactory grain structure, as was noted in connection with FIGURE 8. Further, it is to be seen that the welding or electrode may be positioned either in alignment with the valve stem axis or in a position off-center therefrom, and in either case an essentially non-destructive bond is obtained, as well as permitting the normal manufacturing variations without interference to 'the highly desirable results obtained therefrom.

Various modifications may be. effected in the processes and structuresherein disclosed without departing from the novel concepts of the present invention.

1 claimas my invention:

1. A method of providing a wear resistant tip upon the flat'end face of the impact end of a poppet valve stem, which comprises supporting the valve in an essentially upright position and forming a pool of molten stem material upon the impact end thereof, melting a high carbon alloy having a harder characteristic than the stem onto the pool of stem material, and fusing the molten alloy upon the pool to form a Wear resistant tipintegral with the stern and essentially entirely covering the impact end thereof. 7

2. A method of providing a wear resistant tip upon the flat end face of the impact end of a poppet valve stem, which comprises supporting the valve in an essentially upright position and forming a pool of molten stem material upon the impact end thereof, melting a high carbon alloy having a harder characteristic than the stem onto the pool ofstem material, rotating the valve while forming said pool and melting the alloy thereon, and fusing the molten alloy upon the pool to form a wear resistant tip integral with the stem and-essentially entirely covering the impact end thereof.

3. A method of providing a wear resistant tip upon the flat end face of the impact end of a poppet valve stem, which comprises supporting the valve in an essentially upright position and directing a highly concentrated heat source against the impact end to form :a, pool of molten stem material, maintaining said heat source directed against the impact end and melting a high carbon alloy having a harder characteristic than the stem onto the pool of stem material, and terminating the heat source to fuse the molten alloy upon, the pool and form a wear resistant tip integral with the stem and essentially ontirely covering the impact end thereof.

4. A method of providing a wear resistant tip upon the flat end face of the impact end of a poppet valve stem, which comprises supporting the valve in an essentially upright position and directing a highly concentrated heat source against the radial center of the impact end to form a pool of molten stem material having maximum depth at the point of application of said heat source, maintaining the heat source directed against the impact end and melting a high carbon alloy having a harder characteristic than the stem onto the pool ofstem material, and terminating the heat source to fuse the molten alloy HIPOII the pool and forma wear resistant tip integral with the stem andhaving its maximum depth along the stem axis.

,5. A method of providing a wear. resistant tip upon the flat end face of the impact end of a poppet valve stem, which comprises supporting the valve in an essentially upright position and'clirecting a highly concentrated heat source against the impact end outwardly of the radial center thereof to form a pool of molten stem material having maximum depth at the point of application of said heat source, melting a high carbon alloy having a harder characteristic than the stem onto the pool of stem material, rotating thevalve while forming said pool and melting the alloy thereon, and terminating the heat source to fuse the molten alloy upon the pool and form a wear resistant'tip integral with the stem and having its maximum depth" radially outwardly of the stem axis.

6. A method of providing a Wear resistant tip upon the impact end of a poppet valve stem, which comprises supporting a valve having an essentially flat impact end loan-upright position beneath a Welding electrode, rotating the valve and applying current to the electrode to melt the metal of said impact end and form a pool of molten stem material, directing weld material in wire form adjacent said electrode and forming globules of said material on the molten pool, and fusing the weld material to the pool to form a wear resistant tip integral with the stem and essentially entirely covering the impactend thereof.

7. A method of providing a wear resistant tip upon the impact end of a poppet valve stem, which comprises supporting a valve having an essentially flat impact end in an upright position beneath a welding electrode, rotating the valve and applying current to the electrode to melt the metal of said impact end and form a pool of molten stem material, feeding a weld wire of an air hardenable high carbon alloy adjacent said electrode and forming globules of said alloy on the molten pool, and terminating the wire feed and forming integral with the stem a wear resistant tip having a Rockwell C hardness of at least 50 without subsequent heat treatment.

8. A method of providing a wear resistant tip upon the impact end of a poppet valve stem, which comprises supporting a valve having an essentially flat impact end in an upright position beneath a welding electrode, rotating the valve and applying current to the electrode to melt the metal of said impact end and form a pool of molten stem material, feeding a weld wire of an air hardenable high carbon alloy adjacent said electrode and forming globules of said alloy on the molten pool, and terminating the wire feed and forming integral with'the stem a wear resistant tip having a Rockwell C hardness of-at least 50 without subsequent heat treatment, said alloy before deposition consisting essentially of up to about 6.5% carbon, up to about 2.75% manganese, up to about 1.75% silicon, up to about 9.0% molybdenum, up to about 35.0% chromium, up to about 0.75% zirconium, up to about 1.75% tungsten, up to about 1.25% vanadium, and the balance substantially iron.

9. A method of providing a wear resistant tip upon the flat end face of the impact end of a poppet valve stem, which comprises supporting the valve in an' essentially upright position and forming a pool of molten stem material upon the impact end thereof while cooling the stem portion of said valve, melting a high carbon alloy having a harder characteristic than the stem onto the pool of stem material, and fusing the molten alloy upon the pool to form a wear resistant tip integral with the stem and essentially entirely covering the impact end thereof. V

10. A method of providing a wear resistant tip upon the flat end face of the impact end of a poppet valve stem, which comprises supporting a valve having an essentially flat impact end in an upright position beneath a welding electrode, cooling the stem portion of the vvalve, rotating the valve and applying current to the electrode to melt the metal of said impact end and form a pool of molten stem material, feeding a weld wire of an air hardenable high carbon alloy adjacent said electrode and forming globules of said alloy on the molten pool, and terminating the wire feed and forming integral with the stem a wear resistant tip having a Rockwell C hardness of at least without subsequent heat treatment.

References Cited in the file of this patent V UNITED STATES PATENTS 1,651,547 Rich Dec. 6, 1927 2,073,178 Rich Mar. 9, 1937 2,193,088 Charlton Mar. 12, 1940 2,301,763 Wagner Nov. 10, 1942 2,407,561 Lincoln Sept. 10, 1946 2,471,948 Gibianet a1. May 31, 1949 Hedlund Ian. 3, 1956 

